Palombiella stephensoni Westblad, a Marine Triclad from Banks Peninsula, New Zealand
[Received by the Editor, May 27, 1954.]
Palombiella stephensoni was collected from Menzies Bay and Governor's Bay, Banks Peninsula. It is found in the intertidal zone of a rocky shore, both underneath stones and in the wet crevices of larger locks at half tide. It corresponds in most respects to the description given by Westblad of P. stephensoni.
Mature specimens and freshly laid sessile cocoons were found in August. The size corresponds to that given by Palombi for Synsiphonium stephensoni from South Africa. The shape of the living specimen is similar also, except for the front end, which is blunt and not pointed as in the South African species. The colour (in the living specimen) is dark grey on the upper surface with reegular patches of pale cream. The underside is pale. The anterior end is orange coloured, with the colour continuing round to the ventral side for a short distance. Just posterior to the orange legion there is a well marked black band running across the dorsal side of the front end of the specimen (Fig. 1). The eyes are surrounded by white patches, and just outside these there is a pale cream area.
The reproductive system corresponds fanaly closely to the description given by Westblad. There are three sexual orifices, one median for the genital atnum, and two lateral for the seminal receptacles. The number of testes, however, is greater, 36–38 in a number of specimens examined. They are ventrally placed and extend from the posterior end of the pharynx to the ovaries (Fig. 2). The penis is more or less cone shaped, being very narrow towards the tip and pointed. The vasa deferentia remain as two separate ducts in the penis and join not far from the tip. There is no vesicula seminalis.
The oviducts join posteriorly to form a common oviduct, which enters ventrally the posterior diverticulum of the genital atrium (vagina). This vagina continues posteriorly as a short duct ending in a branch of the intestine, the ductus genito-intestinalis. The two seminal leceptacles (copulatory bursae) are large, extending from the opening to the anterior end of the genital atrium. Two small ducts, the ducti spermatici, run from the ventral portion of the receptacula to the oviducts just before their junction to form the common oviduct. (Fig. 2). The vitellarium, nervous system and gut are similai to P. stephensoni as described by Westblad. Also similar protozoa were found in the pharyngeal cavity and intestine. The distribution of gland cells is similar.
The differences between the specimens described by Westblad and the New Zealand specimens—viz., number of testes and shape of the front end are not considered by the winter sufficient for the creation of a new species.
Genus Palombiella stephensoni Westblad 1951—Synsiphonium stephensoni Palombi 1938.
Distribution. Tristan da Cunha. Nightingale, Inaccesible (Westblad, 1951), Oudekraal, Port Nolloth, South Africa, Banks Peninsula, New Zealand.
Marcus, E., 1948. Turbellaria do Brasil. Bol. Fac. Fil. Cienc. e. Leti. Univ. Sao Paulo. Zoologia N 13, pp. 159–168.
Palombi, A., 1938. Turbellaria del Sud Africa. Arch. Zool. Itnliano. Vol. 25, pp. 368–383.
Westblad, E., 1951. Turbellarans of Tristan da Cunha. Results of the Norwegian Scientific Expedition to Tristan da Cunha, 1937–1938, No. 21.
Wilhelmi, J., 1909, Tricladen, Fauna u. Flora des Golfes von Neapel. Monogr. Nor. 32.